{"id":10793,"date":"2018-11-09T09:04:58","date_gmt":"2018-11-09T09:04:58","guid":{"rendered":"https:\/\/firewood-express-launch.wdl.co\/?p=10793"},"modified":"2018-11-09T09:15:07","modified_gmt":"2018-11-09T09:15:07","slug":"firewood-moisture-content-all-the-facts","status":"publish","type":"post","link":"https:\/\/www.firewood-express.co.uk\/2025\/firewood-moisture-content-all-the-facts\/","title":{"rendered":"Firewood moisture content, all the facts"},"content":{"rendered":"
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\u00a0<\/p>\n<\/div>\n

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Firewood moisture content is such an important issue, I wanted to write this post exclusively to discuss and explain this important & topical issue.<\/p>\n

Trees obviously contain sap when they are growing, in fact when harvested in the summer they can contain up to 50% or half their weight in water.<\/p>\n

The water is required to carry nutrients up from the roots of the trees through the xylem and the sugars from photosynthesis back down through the phloem.<\/p>\n

Often we will try to procure wood harvested in the winter\u00a0when a lot of the sap migrates to the bottom of the tree.<\/p>\n

So we have fresh cut timber at say 45% moisture. The problem with that for burning is that the fire must evaporate off most of that moisture before it can burn. Evaporating water takes a huge amount of energy (2,584,841J = 617 Kcal per Kg water)<\/p>\n

So you can see wet firewood can only give out a fraction of its energy to heat\u00a0your room<\/p>\n

There are additional issues with burning wet wood related to the amount of steam in the smoke, and the cool flue temperatures. These are the ideal conditions to create creosote<\/b>, especially with softwoods, that will coke your flue, and can ultimately cause chimney fires.<\/p>\n

Incomplete burning of the wood gasses also creates more particulates in the smoke which increases pollution.<\/p>\n

OK, so we appreciate we must remove this moisture from the wood, before we burn it, so what are the methods to do this?<\/p>\n

Primarily, the process is referred to as “seasoning” which is the traditional term for leaving logs to dry naturally over time.<\/p>\n

Nature and time will dry firewood logs, but the law of diminishing returns<\/strong><\/span><\/a> cuts in. It takes proportionally longer to get each percentage point of moisture out.<\/p>\n

\"LawThe law of diminishing returns affect firewood seasoning<\/em><\/p>\n

Wood gives up the first 15% quite quickly and easily, but it then starts to get much harder (except for larch, which I will talk about in a bit).<\/p>\n<\/p>\n

So how dry should logs be before burning?<\/strong><\/p>\n

This is a judgment call, the scientific data does suggest that the benefits of drying keep going right down to bone dry or 0% (Click to access full DEFRA report<\/strong><\/span><\/a> careful 327 pages!).<\/p>\n

However, that just increases the costs of firewood production. Tests have shown that the flue gases become “clean enough” at around 20%. This moisture level has been accepted by the regulating authorities and is the level set by Woodsure as being suitable to be “Ready to Burn”.<\/p>\n

With all the recent press interest in the pollution aspects of wood burning, I tried to bring it all together in this blog post:<\/p>\n

Wood Burning Stoves and Pollution Summary<\/a>
<\/strong><\/span><\/p>\n

So if it takes too much time to get under 20% naturally, how do firewood companies achieve this?<\/p>\n

The answer is by using firewood drying kilns.<\/p>\n

\"Firewood<\/p>\n

These machines burn a fuel, ranging from natural gas, through oil to woodchip, to heat the firewood up in dry air to force out the moisture.<\/p>\n

This process obviously increases the costs and environmental cost of your wood fuel.<\/p>\n

Here at Firewood Express, we have the space to use a hybrid system. We air dry our logs for as long as possible, achieving mid 20% moisture content. Only then do we dry the logs in our kiln.<\/p>\n

We find that given the pre-drying, it is quite straight forward to get the last 5% out. We find that to dry from “Fresh” or “Green” takes too much energy and time.<\/p>\n

We also would like to point out 2 things about our kiln:<\/p>\n

1. It is fired by woodchip, a renewable fuel, including wood waste from our production system.\u00a0\u00a0<\/p>\n

2. We use low temperatures, around 30-40 degC, we believe some of the high temperature kilns “cook” out some of the energy from the wood, creating a product that appears to “flare” away to fast.<\/p>\n<\/p>\n

Larch Firewood and Moisture Content.<\/strong><\/p>\n

Larch is a unique and fantastic wood fuel for many reasons, but the moisture topic is specifically interesting.<\/p>\n

Larch appears to expel its moisture. It can be dried naturally to below 17% moisture content within 4-6 summer months. Achieving a “ready to burn” status very quickly.<\/p>\n

So, this means that larch can help create drier firewood with a lower environmental cost.<\/p>\n

Because it is so quick, during the summer months, we offer a\u00a0semi-seasoned larch<\/a><\/strong><\/span> product for your to finish in your own log store.<\/p>\n

So in summary, this is really the most important feature of firewood, with greatest impact on burning qualities. So look out for declared moisture content below 20%, but consider buying larch in the summer months for DIY drying\/seasoning.<\/p>\n

Click to view all Ready To Burn Firewood Options<\/a><\/strong><\/span><\/p>\n<\/p>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

\u00a0 Firewood moisture content is such an important issue, I wanted to write this post exclusively to discuss and explain this important & topical issue. Trees obviously contain sap when they are growing, in fact when harvested in the summer they can contain up to 50% or half their weight in water. The water is …<\/p>\n","protected":false},"author":1,"featured_media":10806,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[169],"tags":[],"class_list":["post-10793","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-current-news"],"acf":[],"yoast_head":"\nFirewood moisture content, all the facts | Firewood Express Uk - Ready To Burn Firewood<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.firewood-express.co.uk\/2025\/firewood-moisture-content-all-the-facts\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Firewood moisture content, all the facts | Firewood Express Uk - Ready To Burn Firewood\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.firewood-express.co.uk\/2025\/firewood-moisture-content-all-the-facts\/\" \/>\n<meta property=\"og:site_name\" content=\"Firewood Express UK\" \/>\n<meta property=\"article:published_time\" content=\"2018-11-09T09:04:58+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2018-11-09T09:15:07+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.firewood-express.co.uk\/2025\/wp-content\/uploads\/2019\/10\/blogs_posts-45.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"480\" \/>\n\t<meta property=\"og:image:height\" content=\"318\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"Elliot Smith\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Elliot Smith\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"4 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.firewood-express.co.uk\/2025\/firewood-moisture-content-all-the-facts\/\",\"url\":\"https:\/\/www.firewood-express.co.uk\/2025\/firewood-moisture-content-all-the-facts\/\",\"name\":\"Firewood moisture content, all the facts | Firewood Express Uk - 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